Image-guided surgery (IGS) is a technique wherein a computer is used to obtain a real-time correlation of the location of an instrument that has been inserted into a patient's body to a set of preoperatively obtained images (e.g., a CT or MRI scan) so as to superimpose the current location of the instrument on the preoperatively obtained images. In a typical IGS procedure, a digital tomographic scan (e.g., CT or MRI) of the operative field is obtained prior to surgery. A specially programmed computer is then used to convert the digital tomographic scan data into a digital map. During surgery, special instruments having sensors (e.g., electromagnetic coils that emit electromagnetic fields) mounted thereon are used to perform the procedure while the sensors send data to the computer indicating the current position of each surgical instrument. The computer correlates the data it receives from the instrument-mounted sensors with the digital map that was created from the preoperative tomographic scan. The tomographic scan images are displayed on a video monitor along with an indicator (e.g., cross hairs or an illuminated dot) showing the real time position of each surgical instrument relative to the anatomical structures shown in the scan images. In this manner, the surgeon is able to know the precise position of each sensor-equipped instrument without being able to actually view that instrument at its current location within the body.
Examples of commercially available electromagnetic IGS systems that have been used in ENT and sinus surgery include the ENTrak Plus™ and InstaTrak ENT™ systems available from GE Medical Systems, Salt Lake City, Utah. Other examples of electromagnetic image guidance systems that may be modified for use in accordance with the present invention include but are not limited to those available from Surgical Navigation Technologies, Inc., Louisville, Colo., Biosense-Webster, Inc., Diamond Bar, Calif. and Calypso Medical Technologies, Inc., Seattle, Wash.
When applied to functional endoscopic sinus surgery (FESS) the use of image guidance systems allows the surgeon to achieve more precise movement and positioning of the surgical instruments than can be achieved by viewing through an endoscope alone. This is so because a typical endoscopic image is a spatially limited, 2 dimensional, line-of-sight view. The use of image guidance systems provides a real time, 3 dimensional view of all of the anatomy surrounding the operative field, not just that which is actually visible in the spatially limited, 2 dimensional, direct line-of-sight endoscopic view. As a result, image guidance systems are frequently used during performance of FESS, especially in cases where normal anatomical landmarks are not present, in revision sinus surgeries or wherein the surgery is performed to treat disease that abuts the skull base extends into the frontal or sphenoid sinus, dehiscent lamina papyracea and/or orbital pathology.
Additionally, a procedure for balloon dilation of the ostia of paranasal sinuses has been developed, wherein a guidewire is advanced into a diseased paranasal sinus and a balloon catheter is then advanced over the guidewire to dilate the ostium of that paranasal sinus, thereby improving drainage from the diseased sinus (Balloon Sinuplasty™ system, Acclarent, Inc., Menlo Park, Calif.). Parent application Ser. No. 11/116,118 describes a variety of sensor equipped devices including sensor equipped guidewires that are useable in performance of the procedure using Balloon Sinuplasty™ tools under image guidance in conjunction with an IGS system.
There remains a need in the art for the development of improved sensor equipped instruments and devices for use in IGS procedures.